Spark ignition direct injection (SIDI) combustion systems (and other direct injection combustion systems) for internal combustion engines provide improved fuel economy and increased power over conventional port fuel-injected combustion systems. A SIDI engine includes a high pressure fuel injection system that sprays fuel directly into a combustion chamber. The fuel is directed to a specific region within the combustion chamber. As a result, a homogeneous or stratified charge may be created in the combustion chamber as desired. Throttling requirements are less restrictive and fuel combustion characteristics are improved, thereby improving fuel economy and engine output.
Referring now to FIG. 1, an exemplary SIDI engine 10 includes an engine block 12 that includes one or more cylinders 14. A spark plug 16 extends into a combustion chamber 18. The combustion chamber 18 is defined by a piston 20, the cylinder 14, and a cylinder head 21. The cylinder 14 includes one or more exhaust ports 22 and corresponding exhaust valves 24. The cylinder 14 includes one or more intake ports 26 and corresponding intake valves 28. A fuel injector 30 extends into the combustion chamber 18. One or more of the fuel injectors 30 are connected to a fuel rail 32.
Referring now to FIGS. 1 and 2, the fuel rail 32 provides fuel to the fuel injectors 30. The fuel injectors 30 deliver fuel to the combustion chamber 18 according to performance requirements of the SIDI engine 10. Typically, a low pressure (e.g. approximately 45-75 psi) fuel supply pump 40 is located within a fuel tank 42. The low pressure fuel supply pump 40 delivers fuel to a high pressure injection pump 44. The injection pump 44 pressurizes the fuel at approximately 750 to 2250 psi, depending on demand. The injection pump 44 provides the pressurized fuel to the fuel rail 32. The fuel rail 32 is rigidly fastened to the cylinder head 21 of the cylinder 14. For example, the fuel rail 32 is fastened to the cylinder head 21 via a fuel rail attachment assembly (not shown). The fuel injector 30 is rigidly fastened (e.g., clamped) between the fuel rail 32 and the cylinder head 21, or another suitable fixture of the SIDI engine 10. A location of the fuel injector 30 relative to the combustion chamber 18, as well as a design of a fuel injector nozzle 46, are optimized to achieve desired combustion characteristics.